1. Field of the Invention
The present invention relates to a method of forming an image on an image-carrying body in an image forming apparatus such as a copying machine, a laser printer and an LED printer, and an apparatus therefor.
2. Description of the Related Art
Generally, in an image forming apparatus such as a copying machine, a laser printer, and an LED printer for performing charging, exposure, developing, transferring, discharging, and the like on an image-carrying body and forming an image on transfer paper or the like, the surface resistance of the image-carrying body is reduced, especially in a high humidity atmosphere, and therefore the charging amount is reduced upon use for a long time period. When the charging amount is reduced, the image is blurred or obscured to cause an image flow, and finally image formation itself becomes impossible. This phenomenon occurs because a corona discharger is used in steps of charging, transferring, peeling, discharging, and the like. The corona discharger can uniformly perform charging of the image-carrying body and rarely causes insulation destruction of the image-carrying body. While the corona discharger has such advantages, it generates toxic substances such as ozone, metal oxides, and an oxygen compound during high energy discharging and oxidizes nitrogen in air to finally form nitrate ions. The nitrate ions are adhered on the surface of the image-carrying body to cause ionic conduction in the presence of water, thereby reducing the surface resistance of the image-carrying body.
The image flow phenomenon rarely occurs in a conventional image-carrying body using an inorganic photoconductive material such as selenium, selenium-tellurium, and cadmium-sulfide or a single layer type or function separating type organic photoconductive material.
An image-carrying body which is currently developed uses amorphous silicon (to be referred to as a-Si hereinafter) or microcrystalline silicon (to be referred to as .mu.c-Si hereinafter) which has higher surface hardness and superior abrasion resistance and heat resistance than those of the above photoconductive material, need not be recovered because it has no toxicity, and has high sensitivity throughout a wide region from a visible range to an infrared range. However, in such an image-carrying body, the image flow occurs more easily than in the conventional image-carrying body. For this reason, this image-carrying body cannot be used for a long time period.
This is partially because a-Si or .mu.c-Si is formed by plasma CVD and therefore has fine projections and depressions on its surface. That is, the surface unevenness increases the number of adsorption sites or adhesion site of the corona discharge product and makes it difficult to remove the corona discharge product by a mechanical removing means such as a cleaning blade. Another reason for this is that a-Si or .mu.c-Si has a surface hardness much higher than that of the conventional photoconductive material. Therefore, unlike in the conventional photoconductive material, the corona discharge product is not removed from the surface by being scraped by a cleaning blade.
In order to eliminate the above drawbacks of the image-carrying body using a-Si or .mu.c-Si, the surface of the image-carrying body is heated so that the image-carrying body does not absorb water, the surface of the image-carrying body is made hydrophobic, the cleaning method is improved, or the image-carrying body is contacted with ion-exchange material. However, a sufficient effect has not been obtained yet.